How to calculate permutations of group labels with R?

Question

Given a vector like:

labels <- c(1,2,3,3,3)

How to get all possible group relabelings? For this example:

1,2,3,3,3
1,3,2,2,2
2,1,3,3,3
2,3,1,1,1
3,1,2,2,2
3,2,1,1,1

I have been looking at the permute package but I don't see how to apply it to this case.

http://stackoverflow.com/questions/7906332/how-to-calculate-combination-and-permutation-in-r — Khashaa, Apr 15 '15 at 15:04
The `do.call(rbind,permn(labels))` should give more rows than the expected result. — akrun, Apr 15 '15 at 15:23
@akrun yes, I would need only the $n_groups !$ re-labelings corresponding to group labels, not the $n_points!$. — alberto, Apr 15 '15 at 15:33
Yup, the **permute** can't do this type of permutation yet. This has come up in some other contexts so I'm looking to add this type of permutation to the package, but I'm crazy busy with the day job for the next couple of months. — Gavin Simpson, Apr 16 '15 at 01:55
Do not add the solution to your question. Instead you should add an answer. — shadow, Apr 16 '15 at 09:53
There is a one line solution by the package iterpc. http://randy.city/iterpc/ — Randy Lai, Apr 22 '15 at 08:42

Khashaa · Accepted Answer · 2015-04-16T08:38:22.813

How about this solution

labels <- c(1,2,3,3,3)
library(data.table)
a <- do.call(cbind, combinat::permn(unique(labels)))
data.table(a)[,lapply(.SD, function(x)x[labels]),]
#   V1 V2 V3 V4 V5 V6
#1:  1  1  3  3  2  2
#2:  2  3  1  2  3  1
#3:  3  2  2  1  1  3
#4:  3  2  2  1  1  3
#5:  3  2  2  1  1  3

Or, just

apply(a, 2, function(x) x[labels])
#     [,1] [,2] [,3] [,4] [,5] [,6]
#[1,]    1    1    3    3    2    2
#[2,]    2    3    1    2    3    1
#[3,]    3    2    2    1    1    3
#[4,]    3    2    2    1    1    3
#[5,]    3    2    2    1    1    3

score 0 · Answer 2 · answered Apr 16 '15 at 11:01

I post here my own solution as suggested:

library(combinat)

labels <- c(1,2,3,3,3)

group.perms <- permn(unique(labels)) 
for(i in 1:length(group.perms)){
  cat(match(labels, group.perms[[i]]), "\n")
}

#2 1 3 3 3 
#3 1 2 2 2 
#3 2 1 1 1 
#2 3 1 1 1 
#1 3 2 2 2 
#1 2 3 3 3

(but I like the second solution proposed by @Khashaa better)

How to calculate permutations of group labels with R?

2 Answers2

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